1. Field of the Invention
This invention relates to a reflective type liquid crystal display in which merging of colors caused by a parallax is not present, a high contrast can be attained, a superior displaying quality is provided and its stable driving can be realized.
2. Description of the Prior Art
In general, as a displaying form of a liquid crystal display, there are provided an opaque type display having a back-light, a transparent type display and a reflective type display. The reflective type liquid crystal display is a liquid crystal display in which only external light such as a solar light and an illumination light or the like is utilized to perform a displaying operation without applying any back-light, and the display of this type is frequently used in a thin portable type information terminal equipment in which a light weight and a low consumption power are required, for example.
FIG. 10 is a sectional view for showing a schematic configuration of the general prior art reflective type liquid crystal display, wherein this display is an example of an STN reflective type liquid crystal display of a simple matrix system, in particular.
This reflective type liquid crystal display has a schematic configuration in which a liquid crystal cell 72 for a reflective mode STN (Super-Twisted Nematic) system and a phase difference plate 73 are laminated on a lower deflector plate 70 of a reflector plate 71 with a lower deflector plate 70, and a front deflector plate 74 is also laminated on this phase difference plate 73.
The aforesaid liquid crystal cell 72 has a schematic configuration in which a lower glass substrate 75, a color filter layer 76, a lower transparent electrode layer 78, a lower orientation film 79, an upper orientation film 80, an upper transparent electrode layer 81 and an upper glass substrate 82 spaced apart and oppositely arranged against the lower orientation film 79 are laminated in this order and an STN liquid crystal layer 83 is arranged between the aforesaid lower and upper orientation films 79, 80.
The aforesaid phase difference plate 73 is used for preventing a display from being colored in blue or yellow by accommodating a phase difference of light passing through the STN liquid crystal.
In the aforesaid prior art reflective type liquid crystal display, light incident to the front deflector plate 74 is linearly deflected by the deflector plate 74 and as the deflected light passes through the liquid crystal layer 83, it is changed into an ellipse deflected light, wherein the deflected light is approached to a linear deflected light under application of the phase difference plate 73 and further the light is linearly deflected through the lower deflector plate 70. The deflected light is reflected by the reflector plate 71, passes through the liquid crystal layer 83 and is outputted from the front deflector plate 74 in the same manner as that of the incident light. A white display and a black display are changed over under an application of voltage and in the case that the white display is carried out, a direction of deflection before incident to the lower deflector plate 70 is coincided with a direction of a deflection axis of the lower deflector plate 70, and in the case that the black display is carried out, they are crossed at a right angle.
However, in the prior art reflective type liquid crystal display shown in FIG. 10, although the display had some advantages that a consumption power can be reduced due to no requirement of a power supply for a back-light in addition to its thin-size and light weight features, it had a problem that its light display was slightly darkened as compared with that of the transparent type liquid crystal display having a back-light of high brightness.
In order to solve the aforesaid problems, there has been proposed that the lower deflector plate 70 arranged between the reflector plate 71 and the lower glass substrate 75 is removed and application of only one front deflector plate 74 arranged on the upper glass substrate 82 causes the light display to be bright at the time of selective application of voltage. However, in such a reflective type liquid crystal display as described above, since only one deflector plate is reduced, it may produce a problem that not only the light display is made bright, but also the dark display is made bright to cause their contrast to be decreased.
In view of the foregoing, the present applicant has shown, as a proposal in Japanese Patent Application No. Hei 9-36720, a reflective type liquid crystal display having a bright display in which a reflector, a color filter, a transparent electrode layer and an orientation film are arranged in sequence on the opposing surface of a lower glass substrate, a transparent electrode layer and an orientation film are arranged in sequence on the opposing surface of the aforesaid upper glass substrate, a first phase difference plate and a second phase difference plate are arranged in sequence on the outer surface of the upper glass substrate, a liquid crystal layer is arranged between the orientation films of the upper and lower glass substrates, and further a product .increment.nd of anisotropy of refractive index .increment.n of a liquid crystal and a layer thickness d of a liquid crystal, a relation between phase differences R.sub.1, R.sub.2 of each of the first and second phase difference plates or an angle of a deflecting axis of the deflector plate or an angle of a lagging axis of the first and second phase difference plates are limited to a specified range. In addition, it is preferable to use a reflector member that, as the reflector member installed in such a reflection type liquid crystal display having the aforesaid configuration, some fine corrugated (concave or convex) portions are formed on the surface of the lower glass substrate in order to increase a visual angle, a metallic reflective film such as either an Al film or Ag film or the like is formed on the corrugated surface, thereby the surface of the metallic reflective film is provided with the corrugated surface acting as a reflective surface.